Artificial silk and process of making same



Dec. 9

. 1,517,627 E. HUBERT ARTIFICIAL SILK AND PROCESS OF MAKING SAME FiledDec. 23. 1922 Gumm Patented Dec. 2, 353924.

UNITED STATES PATENT OFFICE.

EMIL HUBERT, O'F ELLBERFELD, GERMANY. ASSIGNOR TO FARBENFABRIKEN VORM.

FRIEDR. BAYER AND 00., OF LEVERKUSEN. NEAR COLOGNEONTHERHINE, GER- MANY.

ARTIFICIAL SILK AND PROCESS OF MAKING SAME.

Application filed December 23, 1922. Serial No. 608,747.

To all whom it may concern:

Be it known that I, Earn. I-Irnunr. a citizen of Germany, residing atElberfeld, Roonstrasse 28, in the State of Prussia. Germany, haveinvented new and useful Improvements in Artificial Silks and Processesof Makin Same, of which the following is a speci cation.

The United States Letter Patent- No. 710,- 819 describes a process forthe manufacture of artificial silk in which comparatively thickfilaments formed from an ammoniacal copper oxide solution of celluloseare led through two superposed layers of liquid at differingtemperatures, the filaments being drawn out mainly in the slowly actingprecipitating layer, which has a temperature of 40-50 C. andprecipitated and hardened in the rapidly precipitating layer which has atemperature of 95100 C.

The solutions of many valuable materials cannot be treated by thisprocess even if the filaments so produced are further treated: this isespecially the case for such solutions which on'the one hand do notallow com-- paratively thick filaments to be drawn out to very finefilaments at the lower temperature employed, but which possess suchproperty only at" a high temperature, and which on the other hand at therequisite temperature of the precipitating baths are precipitated asmilk white, tender filaments which are therefore worthless.

Heretofore it has beenimpossible to utilize the solutions of suchmaterials in the manufacture of artificial silk where it was desiredthat individual filaments should have a fineness of 1-2 deniers, it hasonly been possible if at all to manufacture filaments of a stoutness of20 deniers and more unless capillary nozzles 0.1 mm. and less in widthwere employed. The large range of cellulose esters and ethers belong tothis class.

By this invention filaments having the fineness of cocoon silk can bemade from the solutions of such materials with the employment ofcomparatively wide orifices by leading the comparatively thick filamentsthrough two layers of liquid of which the first is hotter than thesecond.

lit will be observed that this is the direct opposite to the knownprocesses of drawing fi aments in which the comparatively thick filamentis led through two liquid layers of which the first is colder than thesecond and so in this process, ology of the Patent No. 710,819, on thecontrary first employ a rapidly acting precipitating medium and thenaslowly acting precipitating medium. This inversion alone renders itpossible to manufacture the finest artificial silk from solutions ofsuch substances. The column of the liquid layers of the type ofliquidemployed-depends on the character of the substances used; thetemper? ature of the first layer of liquid must, however, be such thatfilaments are not fractured by drawing them out to the requiredfineness, while its column should be so short that during the drawingout process the filaments are not largely precipitated and so enterthesecond layer in a semi-solid state where they gradually harden byprolonged contact with the colder liquid.

The drawing apparatus employed may be those now in use.

If due to a difference in specific gravity between the solution and theprecipitating liquids, it is necessary to squirtfthe solution upwards,the lower layer or liquid must be hotter and have a higher specificgravity than the upper layer of liquid; when on the contrary thefilaments are drawn in a downward direction out of nozzles, the upperlayer is hotter and has the lower specific gravity. The first layer maybe brought to and maintained at the required temperature by a heatingworm, or fresh hot liquid may be added slowly to the bulk of the hotliquid. Preferably the second layer circulates continuously to impart toit a movement in the direction of the issue of the filaments. Whennecessary means may be provided for aiding the maintenance of theseparation of the two layers of liquid and for preventing eddy currentsat the surfaces of contact.

EwampZe.-A cellulose acetate soluble inacetone is dissolved in drypyridine bases to form a homogeneous 20-25% solution which afterfiltration is led to the nozzle of an apparatus such, for example, asthat described in British Letters Patent No. 14655 of 1907; Apparatussuitable for carrying out the process is illustrated diagrammatically inthe accompanying drawing. In the nozzles 2 there may be holes of 0.6

to employ the phrase-- min. each. After the apparatus has been filledwith cold water, hot water at 60 C. is delivered through the upper inlet1 at the rate, for example, of -50 0. cms. per minute and contacts withthe thick filaments issuing from the nozzles 2 in a downward directionsuch layer being 35 cm. long and possessing a temperature of 45-55 C.Water at 1015 C. is delivered through the lower inlet 3. If the funnel4-. together with its leg 5 is 25-30 cm. long then the inlet of 300-5000. cms. of water per minute suffices for a draw velocity of 40 metresper minute.

Inthe hot water zone the comparatively thick filaments passing into thefunnel 4: are first stretched by gravity alone but subsequently they aredrawn out by the pull of the water flowing in the leg 5 of the funneland by the winding apparatus 6 to the fineness desired, and enter thecold water zone in a semi-solid and viscous condition; the filamentssolidify in this zone and when drawn off by the winding apparatus 6 havea glossy appearance. The winding apparatus 6 may, if desired, for thepurpose of removing any traces of pyridine from the filaments, rotate inthe air or in a bath of water or dilute acid.

When dry, the filaments are in a condition to undergo any furthertreatment and each individual filament may have a fineness of 2-3deniers. When stouter filaments are made, they may often, to commencewith,

appear to have an opal gloss, but this disappears on drying. Although inthis example the diiference in specific ravity between hot and coldwater is smafi, yet after a few minutes there is a definite line ofseparation between the liquid layers. In order to enhance the drawingproperties of a solution of cellulose acetate in pyridine, smallquantities of suitable substances may be added; thus the addition of10-30% acetylenetetrachloride C H CI, relative to acetate renders thesolution of higher specific gravity and more easily drawn, theindividual filaments coming away from the nozzle more easily, thusallowing finer filaments to be obtained.

The process is not limited to the substances described and for exampleviscose and an ammoniacal copper oxide solution of cellulose asdescribed in the Patent 710,810 may with advantage be employed.

I claim The manufacture of artificial silk by a drawing process of thetype employing two superposed liquids at different temperatures and ofdifferent specific gravities, in which comparatively thick filamentspass first into the hotter liquid where they are drawn and then into thecolder liquid, substantially as described.

In testimony whereof I have hereunto set my hand.

EMIL HUBERT.

